In recent years, the vast majority of the industrialized world has become telephonically accessible via the public switched telephone network (PSTN). Most commonly, this accessiblity has been implemented through conventional telephone systems. A conventional telephone system may be considered to be and is hereinafter included in the general category of wireline systems, i.e., telecommunications systems that transmit communications over lines such as copper or fiber optic lines. Thus, a unit that operates in a wireline system may be referred to as a wireline unit.
Convenient devices such as cordless telephones have been developed to work with the PSTN and to facilitate communications. The term "cordless telephone" is an appropriate appellation to the device to which the term refers. A cordless telephone is a telephone with no cord between the handset and the base. Each piece typically contains a radio transmitter, a receiver, and an antenna. The handset contains a rechargeable battery; the base plugs into a power source and is functionally connected by a wireline system to the PSTN. As a result of this connection by wireline system to the PSTN, a cordless telephone is considered to be a wireline unit. Advantageously, the cordless telephone allows the user to communicate through use of the handset, and further allows the user to communicate through use of the handset and to range several feet and in some cases up to several miles away from the base. Based on this advantage of mobility, cordless telephones have been welcomed by users and such devices may be found in many homes and other places.
The advantage of communication on the move is also a characteristic of a cellular mobile radiotelephone (CMR) system. But CMR systems typically allow a user a far greater range of movement than cordless telephones. In CMR systems, the user is not tied in any way to a base such as the base used in cordless telephones. In some cases, a CMR system may provide a user with an unlimited range of use. In a typical CMR system, a user makes use of a cellular mobile radiotelephone to receive and transmit communications without being limited to a fixed location. A cellular mobile radiotelephone is also referred to herein as a "cell phone". CMR systems typically operate in addition to and through the PSTN to provide users with these additional communication services and advantages.
The popularity and widespread acceptance of CMR systems have brought about the development of systems that work as an adjunct with CMR systems and with the PSTN. An example of an adjunct to CMR systems is the fixed wireless (FWL) system. An FWL system allows a user to effectively convert certain conventional telephones into extensions of the user's cell phone. In particular, an FWL system usually includes a cell phone physically connected to one or more conventional telephones within a discrete location, such as a home or office. The FWL system allows the user to make use of the CMR system through the connected conventional telephones. These extensions to the cell phone may provide the user with certain advantages. Yet, these FWL systems do not provide the user with access to the PSTN independently of the CMR system. Such lack of direct access to the PSTN could be critical in the event that one of the wireless communication links, from and including the cell phone to the CMR system, is not functioning properly. Another example of an adjunct to CMR systems is a type of system referred to herein as "base station" technology, but also commonly known as "cellular cordless" technology. Base station technology allows a user to make use of certain aspects of conventional telephone systems and of CMR systems. To utilize this base station technology, a user who has access to the PSTN and who also has access to a CMR system must purchase both a specially equipped base station and a specially equipped cell phone. Such equipment is manufactured by Motorola Inc., 600 North U.S. Hwy 45, Libertyville, Ill. 60048 and available as a Personal Phone Series (PPS) system. The base station is located typically at the user's base of operation, be it a residence, office or the like. The base station is connected to the PSTN and includes a mechanism for detecting the proximal presence of the user's cell phone when that cell phone is within a certain limited geographical distance of the base station. In essence, the base station functions as a cell site which provides a continuous "control channel" in a manner similar to a conventional cell site. The base station is different from the conventional cell site in that it utilizes a non-standard control channel that changes based on internal interference avoidance algorithms. Additionally, the base station uses a narrow band channel with a 200 bits per second data carrier.
Normal operation of the specially equipped cell phone includes a periodic scan of the designated control channel to determine whether the cell phone is within range of the the base station. If so, the cell phone and base station "handshake" in a manner well known in the telecommunications field. The result of the handshake is registration of the cell phone with the base station, which registration triggers an operational switch to the cell phone operating with the base station. The CMR system is then notified of the registration. Typically, the base station then functions as a wireline unit and is assigned a wireline number. Accordingly, after the CMR system is notified of the registration of the cell phone with the base station, the CMR system does not accept or continue handling the communication directed to the number associated with the cell phone in the conventional manner. Instead, the CMR system effectively relinquishes the communication to the PSTN. Thereafter, the communication is routed in a conventional manner through the PSTN to the base station.
In response to receiving the communication through the PSTN, the base station transmits the communication to the cell phone in much the same manner as a communication would be transmitted to a cordless telephone in a wireline system. Effectively, the cell phone functions as a cordless telephone. By this relay of the communication, the CMR system is not involved in connection of the communication. Thus, expenses associated with cellular services and usage fees are obviated with respect to this communication. In other words, even though this communication was initially directed to a number associated with a cell phone, the communication is ultimately connected as a conventional telephone call or wireline call. Thus, the user is not charged cellular service charges for the communication.
In sum, base station technology allows increased flexibility for a user because the user may use a cell phone in a manner that does not incur the significantly higher usage fees typically accompanying cell phone use. The benefits of base station technology, though, are predicated upon several factors. First, the user must purchase a specially equipped cell phone and also purchase an accompanying specially equipped base station. Second, the cell phone must be within proximal range of its base station. Even after these criteria are met, a user must still provide two telephone exchange numbers--one for the cellular service and one for the landline service. Finally, an individual who desires to implement base station technology will, after purchasing the specialized base station and cell phone, likely be left with a conventional cordless phone which is unusable in conjunction with the base station technology.
Accordingly, there is a need to provide a user who has access to the PSTN and also subscribes to a CMR service with a way to receive a wireless communication through a wireline system in a reliable and more cost-efficient manner than currently available. Specifically, there is a need to provide such a service without requiring purchase of a specially equipped cell phone or a specially equipped base station. Furthermore, there is a need to provide such a service without requiring a user to provide different telephone exchange numbers to individuals who may be interested in calling the user at a "home" location. Finally, there is a need to provide such a service that will incorporate existing personal communication hardware, such as conventional cordless phones, rather than replace them, thereby rendering such devices obsolete.